The assignee of the present invention manufactures and deploys spacecraft for, inter alia, communications and broadcast services. Spacecraft often include various deployable structures, e.g., solar arrays, antenna reflectors, antenna masts, etc. Such structures may, for example, often be folded flat against a side of the spacecraft during launch and may then subsequently be deployed using, for example, positioning mechanisms when the spacecraft is on-orbit. The positioning mechanisms may also be used, in some cases, to re-orient such deployable structures after the spacecraft is on-orbit.
Due to the fact that the deployable structures are typically only operationally deployed in the zero-gravity environment experienced when the spacecraft is on-orbit, the positioning mechanisms used are preferably designed for lower loads than might be the case were they intended to be operational in a 1 G field. This allows a positioning mechanism to be smaller and to have a reduced weight than it might have in a normal Earth-gravity environment. However, while the spacecraft is generally in a weightless environment once on-orbit, such is not the case during launch. In a launch environment, the spacecraft may experience accelerations of multiple G's that may exert forces on the deployable structures that are beyond the positioning mechanism's ability to withstand and that may result in damage to the bearings, motors, or other components of the positioning mechanism. One current practice to avoid damaging the positioning mechanism for a deployable structure on a spacecraft is to temporarily anchor the deployable structure to the spacecraft body using one or more releasable standoffs, e.g., frangible bolts. Such arrangements may be referred to generically as “caging mechanisms”.
The present inventor has recognized that there is a need for positioning mechanisms that may replace one or more such releasable standoffs.